1. Field of the Invention
The present application relates to an optical transmitter module implementing a plurality of optical sources.
2. Background Arts
An optical transmitter module, the optical power output therefrom and detected through an optical fiber coupled with the optical transmitter module sometimes exceeds a preset magnitude in a case where a laser diode (LD) installed in the optical transmitter module is adequately aligned with the optical fiber. Decreasing the bias current supplied to the LD to reduce the optical power, the LD degrades high-frequency performance thereof due to a decrease of the resonance frequency. Accordingly, the coupling efficiency between the optical fiber and the LD may be adjusted by shifting the optical fiber from a position at which the optical fiber and the LD shows a maximum coupling efficiency, which is often called as de-focusing.
When the optical transmitter module implements a plurality of channels (or lanes) each including an LD that emits light with a wavelength specific thereto and different from others, such plurality of optical signals are multiplexed and couple with one optical fiber. When the de-focusing described above is performed for one channel, or between one LD and the optical fiber, the other LDs or the coupling efficiencies between the other LDs and the optical fiber do not always satisfy the requested specification. Usually, the output power detected through the optical fiber and originated to the other LDs exceeds the preset limitation or become insufficient.